At about the same time, MSI completed a 2.2-mile stretch of Hwy. 150 in Henry County using a Type III mix design requiring a 36-pound dry aggregate content. On this particular 10-year-old pavement, which had a CRS rating of 6.6 (good condition), IDOT requested additional aggregate to compare how the two different projects would perform. The project contract was $119,115.
Time will tell
On the Knox County Hwy. 150 project, Ritschel estimates the microsurfacing will extend the road's life cycle five to seven years. During application, IDOT officials monitored application rates and will conduct their own evaluation of how the treatment performs over time. The agency is particularly interested in how the surface treatment holds up to a typical harsh Midwest winter.
If the preservation approach proves successful for IDOT, Ritschel estimates significant savings in maintaining road quality for the state. According to Ritschel, micosurfacing a road that's in fairly good condition costs approximately $18,000 per mile, while a typical mill and fill (milling off the surface mat and applying a new hot mix asphalt mat) can cost approximately $36,000 per mile, and a full-depth rehabilitation can cost upward to $200,000 per mile.
"Most states are in that 'worst first' mode of maintaining existing roads. They are reluctant to invest in roads that are in good condition, with the understanding that the investment will eventually reduce the overall costs of major rehabilitation, because the roads will last longer," Ritschel says. "The biggest dilemma with a product like microsurfacing is that it has to be applied in a preservation mode in order to extend the life cycle of the road. If the road is in bad condition, a preservation approach is not going to help. And agencies find it difficult to invest in roads that are in good shape, when taxpayers want the worst roads fixed first."
While Illinois and Missouri are in their infancy with preservation pavement projects, Ritschel says both are optimistic on how the approach can help maintain quality roads, stretch budgets and free up available funds for new and major rehabilitation projects.
"The state (IDOT and legislators) has taken the initiative to endorse a preservation approach even though it does not provide immediate savings, but rather long-term savings by extending a road's life cycle," Ritschel says. "They (IDOT) understand how an investment in preserving good roads can pay dividends in the future. IDOT is incorporating familiar preservation techniques (like crack sealing) with unfamiliar preservation techniques (like microsufacing) into their 'mix of fixes.' We're (preservation proponents) trying to provide maintenance activities in ways that lower life cycle costs, thereby saving the agencies money and making taxpayers happier."